A new report says there are no health or environmental risks from gas bubbling to the surface of a Queensland river close to coal seam gas sites.
But there's still no definitive explanation of the cause of the gas seepage, which has left stretches of the Condamine River bubbling like a spa bath.
Anti-coal seam gas campaigners released dramatic footage of the phenomenon in May last year.
Lock the Gates Alliance president Drew Hutton suggested it may be linked to coal seam gas mining in the area.
Natural Resources and Mines Minister Andrew Cripps said on Monday the phenomenon had been thoroughly investigated and there was no risk to the environment or to human and animal health.
He said the gas had been found to be predominantly methane, which was consistent with gas originating from Surat Basin geological formations.
Safety testing had been carried out at four gas seeps and adjacent properties at key sites, along with water and soil sampling at targeted seeps and other sites along the river.
"Analysis of these results has to date found no evidence of gas safety or water quality risks to the community from the gas seeps or any evidence of environmental harm," Mr Cripps said.
The next phase of the investigation will look at gas seeps downstream of Chinchilla Weir.
That will include ongoing water quality monitoring and periodic gas safety assessments of the river and water bores on adjacent properties.
"While the results of this report don't provide definite evidence of the source or cause of the gas seeps, we are taking a long-term approach to find science-based answers to this phenomenon," Mr Cripps said.
He said a separate investigation by coal seam gas company Origin was also under way.
He said a key aspect of government's investigation was to verify data provided by Origin, to ensure the company's investigation is "rigorous and is independently assessed".
"An independent scientific review will be completed by Queensland's Chief Scientist, Dr Geoff Garrett, to ensure that Origin's investigation and verification actions by government agencies, achieve a high scientific standard and integrity," Mr Cripps said.
"All this work will be co-ordinated by the government's LNG Enforcement Unit and adjacent landholders will be kept fully informed about activities and findings."